Antibody-like binding moieties (including those in intact antibodies, antibody fragments, and scFvs) are often used for therapeutic applications. Antibody fragments and scFvs generally exhibit shorter serum half lives than intact antibodies, and in some therapeutic applications increased in vivo half lives would be desireable for therapeutic agents possessing the functionality of such fragments and scFvs.
Human serum albumin (HSA) is a protein of about 66,500 kD and is comprised of 585 amino acids including at least 17 disulphide bridges. As with many of the members of the albumin family, human serum albumin plays an important role in human physiology and is located in virtually every human tissue and bodily secretion. HSA has the ability to bind and transport a wide spectrum of ligands throughout the circulatory system, including the long-chain fatty acids, which are otherwise insoluble in circulating plasma.
The serum albumins belong to a family of proteins that includes alpha-fetoprotein and human group-specific component, also known as vitamin-D binding protein. The serum albumins are the major soluble proteins of the circulatory system and contribute to many vital physiological processes. Serum albumin generally comprises about 50% of the total blood component by dry weight. The albumins and their related blood proteins also play an important role in the transport, distribution, and metabolism of many endogenous and exogenous ligands in the human body, including a variety of chemically diverse molecules, such as fatty acids, amino acids, steroids, calcium, metals such as copper and zinc, and various pharmaceutical agents. The albumin family of molecules is generally thought to facilitate transfer of many of these ligands across organ-circulatory interfaces, such as the liver, intestines, kidneys, and the brain. The albumins are thus involved in a wide range of circulatory and metabolic functions.